1. Field of the Invention
The present invention relates to a color video printer, and more particularly to an apparatus for automatically driving a platen roll and a thermal print head of such a color video printer, in which the platen roll and the thermal print head are driven by means of a cam and levers mechanism in order to shift between the compressed printing position and the stop position at the same time.
2. Description of the Prior Art
Referring to FIG. 1, known color video printers generally comprise a head lever 1 which has a thermal print head secured to a front end thereof, a manipulating lever 2 for causing the head lever 1 to turn about a turning shaft thereof, a film cassette 4 which is capable of being removably mounted into the printer, and containing therein a film which is used for transcribing color images thereof on printing papers 3, and a platen roll 5 for providing a pressing force for the thermal print head of the head lever 1 in order to press the printing paper 3 and the film of the cassette 4 disposed between the platen roll 5 and the thermal print head.
On the other hand, the platen roll 5 is connected, as shown in FIG. 2, to an end of a platen lever 6 of which the other end has an integrally formed sector gear 7, said sector gear 7 then engages with an intermediate gear 8. The intermediate gear 8 also engages with a driving gear 10 which is secured to a driving shaft of a reversible driving motor 9.
In FIG. 1, the reference numerals 11 and 12 denote a pair of rollers oppositely disposed in order to face with each other for resiliently transmitting the printing papers 3 to the printing position, that is, a pinch roller and a grip roller, respectively.
In operation of the known color video printer of the above construction, upon having mounted the film cassette 4 in a place of the printer, the manipulating lever 2 is first manually manipulated in the counterclockwise direction in order to shift from the stop position shown at the solid line of FIG. 1 to the printing position shown at the phantom line of the drawing. In result, an integrally formed protrusion 2a of the manipulating lever 2 downwardly biases the head lever 1, thereby causing the head lever 1 to move from the stop position to the compressed printing position. Thereafter, as the printer is turned on, the printing paper 3 is transmitted to the printing position by virtue of a rolling action of the pinch roller 11 and the grip roller 12. At the same time, the film of the film cassette 4 is disposed at the printing position. In sequence, the driving motor 9 rotates in order to drive the driving gear 10, thereby causing the intermediate gear 8 and the sector gear 7 to rotate. In result, the platen lever 6 rotates clockwise in order to make the platen roll 5 shift upwardly, thereby causing the platen roll 5 to closely contact with the thermal print head of the head lever 1 in order to accomplish the compressed printing standby state.
However, the known color video printer has disadvantage in that it has to be provided with the auxiliary transmitting mechanism for shifting the thermal print head of the head lever 1 and the platen roll 5, thereby causing the construction of the printer to be complex. Furthermore, the known color video printer has another disadvantage in that the manipulating lever 2 for shifting the head lever 1 has to be manually operated, thereby causing the manipulation therefor to be considerably inconvenient.